1. Field of the Invention
The present invention relates to a digital camera provided with a focusing device that automatically focuses a taking lens for photographing an object image.
2. Description of the Related Art
Conventionally, a TTL (Through The Lens) phase difference auto focus (AF) has often been used as an AF mechanism in a lens-interchangeable single-lens reflex camera using a silver halide film or imaging device as an image pick-up medium. In the TTL phase difference AF, a focus detection mechanism is provided in a camera body and, based on a result of focus detection thereof, a focus is adjusted by driving a part or whole of a taking lens provided with the interchangeable lens using a motor mounted inside the interchangeable lens or camera body.
In a compact digital camera or camcorder, on the other hand, an AF mechanism (hereinafter called a contrast AF) adjusting the focus by driving a taking lens so that, after detecting a contrast value of an object image using high frequency components of an image signal obtained by an imaging device, the contrast value becomes maximum is often used.
Generally, the TTL phase difference AF and the contrast AF have different features. For example, the TTL phase difference AF operates at high speed while the contrast AF can detect the focus with high accuracy and thus an appropriate AF is used for each purpose.
In an auto focusing device described in Japanese Patent Application Laid-Open No. 7-43605, for example, when adjusting the focus by combining the contrast AF and TTL phase difference AF, a coarse adjustment is made by the TTL phase difference AF and then a fine adjustment is made by the contrast AF. Also, in an auto focusing device described in Japanese Patent Application Laid-Open No. 2003-302571, if, in focusing processing in which, like Japanese Patent Application Laid-Open No. 7-43605, a coarse adjustment is made by the TTL phase difference AF and then a fine adjustment is made by the contrast AF, a determination is made that focusing can be obtained by the TTL phase difference AF, a faster focusing operation is implemented by making the TTL phase difference AF have higher priority to perform than the contrast AF does.
The TTL phase difference AF cannot detect the focus accurately if a light flux for focus detection used for focus detection is shaded. In a lens-interchangeable single-lens reflex camera or the like, various kinds of interchangeable lenses can arbitrarily be attached and, when a lens whose F number (FNO) is large or a special lens such as a reflecting telephoto lens is attached, a light flux for focus detection of the TTL phase difference AF may actually be shaded.
However, conventional techniques described above do not mention measure to be taken when a light flux for focus detection of the TTL phase difference AF is shaded and, if a coarse adjustment is made by using the TTL phase difference AF, the contrast AF may be made to perform after moving a taking lens to an incorrect position. As a result, an amount of deviation from a focusing position increases and a time required for focusing operation by the contrast AF also increases.